This invention relates generally to electromagnetic locks which are employed in connection with doors for controlling egress and/or access through the door. More particularly, the present invention relates to electromagnetic lock systems which employ an electromagnetic core mounted in a housing and an armature mounted relative to the door and the door frame to automatically control passage through the door.
Electromagnetic locks have been employed for a number of exit door/emergency door applications to provide an effective and reliable means for locking the associated door while also permitting egress through the door in an emergency and other situations. The functions and capabilities of such electromagnetic lock systems have become relatively sophisticated. For example, common features incorporated in conventional electromagnetic lock systems include a time delay to delay unlocking of the lock for a pre-established time interval to enhance security and control egress from the secured enclosure. Various alarms, visible signal devices and monitors also are employed for activation when an attempt is made to egress through the associated exit or emergency door. Electromagnetic lock systems also commonly incorporate devices releasing the electromagnetic lock in case of fire. Conventional electromagnetic lock systems may also automatically generate various signals and instructions at the electromagnetic lock housing for facilitating the use of the electromagnetic lock.
In U.S. Pat. No. 5,065,136, to which the present invention relates, an exit door security system employs an electromagnet and an armature to lock an exit door. A housing for the electromagnet is pivotally mounted to a frame assembly which is in turn mounted to the door frame. An attempt to exit the door causes the housing to pivot to thereby actuate a switch. The lock condition provided by the electromagnet is automatically released after a pre-established time delay. An alarm at the door can also be actuated by the switch. The electronic circuitry may be configured to allow for immediate authorized egress and to implement an immediate safety release for the lock. The lock can be operated in the normally locked or normally unlocked mode. Various alarms and visual indicators and a speech or a voice synthesizer are also incorporated into the electromagnetic lock system. The electromagnetic lock is capable of adjustment to implement time intervals for a nuisance delay, a relock delay, and an egress delay and is capable of operation in response to a number of inputs to the system.